(i)
from variations of the accretion rate onto the planet, which might be on the keplerian timescale around it, \(P\sim 2~\mathrm {d}\times [R/(10~R_{\mathrm {J}})]^{3/2}[M_{\mathrm {p}}/(3~M_{\mathrm {J}})]^{-1/2}\)  at cylindrical radius \(R\) ;
(ii)
from variations of the magnetic field topology, with a timescale linked to the one over which the field-generating gas in the planet's interior moves;
(iii)
from variations of the viewing angle onto the hot spot (through the column or not), over the course of a planetary rotation (\(\sim 10\)  h; [1]}, [2]}, [3]}, [4]}); and
(iv)
from variations of the optical depth along the column, for example from fluctuations in the temperature structure. If the preshock region is transmissive (“optically thin”), its thermal time should set the timescale [5]}; otherwise, the diffusion time is the relevant quantity. Simple estimates of their value is however challenging, but they are likely fast compared to the other, dynamical processes.

